It's your choice. Spend a little time and effort one time now to change the rough-in so you can use a Drake, or spend a little time and effort frequently forever dealing with the AS problems.

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I'll take my chances with the AS rather than dealing with floor joist in the way preventing 12".... Besides this is last room to be remodeled in 1942 built home and I'll probably sell sooner than later. Toto Drakes in next one....

I installed a drake in a 11 inch rough in with the back wall sloped considerably toward the toilet. I installed the tank as far to the front of the bowl as possible(the tank bolts are smaller than the hole in the porcelain), angled the flange bolts toward the front as much as allowed, and shimmed the back up one eighth with waterproof wedges. I Tightened the bolts down a little so the bowl would not move and Then I continued shimming the entire toilet right to the front. Finish tightening the bolts and A thin layer of silicone at the bottom and you would never know. The tank clears the wall but barely. I suppose you could add even bigger shims to the back to make more clearance but you still want to make it look like an adult was at work - a huge angle on the toilet makes you look bad even though it might work. If you are concerned about unequal loading on the base you could set the bowl into a mortar mix